I bulit a set of sysyem, which has 68013A and XC9572XL, the communication between them is used slave fifo, and the flags is in index mode, so the flagb is full flag of all usb fifos and the flagc is empty flag. In firmware, the EP2 is set to 2X out buffer, and it's size is 512. When I sent 512 data from pc to cpld through EP2, the flagb and flagc is both high, when I sent 1024 data or sent 512 data twice, the the flag c is high, and the flagb is low, it means that the fifo of EP2 is full. Cpld is ready to receive the 512 data, when the usb fifo is full only, and stoped when the fifo is empty, but I found that the flag is still full, when the cpld received the 512 data over correctly, and 512 data could not be sent to EP2 next time any more (Even if I reset EP2)using cyconsole. Is the firmware has problem or the cpld program. Thanks a lot!